The present invention relates to a sheet collecting apparatus and collecting method of the apparatus for bearing and storing sheets carried out of a sheet discharge outlet in a post-processing apparatus, an image formation apparatus, etc. and more particularly, to improvements in an aligning mechanism and aligning method for neatly positioning and storing sheets fed onto tray means.
Generally, this type of sheet collecting apparatus has widely been known as an apparatus for bearing and storing sheets fed to a sheet discharge outlet of an image formation apparatus, etc. For example, post-processing apparatuses are known which have a post-processing unit for temporarily bearing sheets from the sheet discharge outlet to collate for each set, and performing post-processing such as binding processing, folding processing and punching processing on a bunch of sheets, and collect sheets with images formed for each set to perform bookbinding stapling, punching filing holes and the like.
When such an apparatus performs post-processing such as binding processing on a bunch of sheets collected for each set on a processing tray, a subsequent sheet may be supplied to a carry-in entrance on the upstream side. For example, Japanese Laid-Open Patent Publication No. 2008-213971 [Patent Document 1] discloses in FIG. 2 a post-processing apparatus for collecting sheets with images formed in the image formation apparatus for each set on the processing tray to staple. Then, a subsequent sheet may be supplied from the image formation apparatus during the operation of performing post-processing such as binding processing on a bunch of sheets collected for each set on the processing tray. It is proposed in the publication that a sheet transport path is provided with a holding section for temporarily holding a sheet, and overlapping the held sheet and a subsequent sheet to concurrently carry out of the sheet discharge outlet.
As described above, when a sheet supplied continuously and a subsequent sheet held in the transport path are overlapped and fed to the processing tray, and aligned by causing the sheets to strike a regulation stopper, conventionally, the sheets overlapped in the transport path and a sheet that is not overlapped are designed to strike the stopper in the same transport mechanism in both of the cases. For example, in the apparatus of Patent Document 1 described above, when a sheet from the sheet discharge outlet is transported toward the regulation stopper by a forward/backward rotation roller on the tray, the transport force that the roller applies to the sheet is controlled under the same condition for sheets that are overlapped and a sheet that is not overlapped.
However, when a sheet and another subsequent sheet are overlapped in the transport path and aligned by striking the stopper, the following problem occurs. When sheets from the sheet discharge outlet 90 are loaded and stored on the tray 91 as shown in FIG. 12, an alignment roller 92 is disposed above the tray, and feeds the sheets toward a rear-end regulation stopper 93, and the sheets thereby strike the stopper and are aligned. At this point, the overlapped sheets are sometimes displaced to the front and back in the shape of scales, or in order for the pages to get out of order in prior and subsequent sheets, the sheets are sometimes made displaced to the front or back. At this point, a sheet end of a prior sheet strikes the stopper, and then, the sheet is sometimes curved and becomes deformed upward above the tray. In this case, a rear sheet that is doubly displaced rises above the tray, and a problem occurs that a sheet jam arises. Particularly, when a sheet-surface pressing guide 94 is disposed between the alignment roller 92 and the rear-end regulation stopper 93, such a problem occurs that the sheet does not enter inside the guide.
It is an object of the invention to provide a sheet collecting apparatus for enabling sheets to be aligned neatly in a predetermined position on a tray even when front ends of the sheets are displaced to the front and back in overlapping the prior sheet Sf and subsequent sheet Sr and carrying the sheets out of a sheet discharge outlet to feed onto the tray.
Further, it is another object of the invention to provide a sheet collecting apparatus enabling sheets to be collected always with stability by varying control operation of an alignment roller for providing the sheet with a transport force between the case of overlapping a sheet and another subsequent sheet in a path to feed onto the tray and the case of feeding a sheet without overlapping with another sheet.